Automatic transmissions are expensive assemblies that include many long-lasting components. However, there are internal components subjected to levels of vibration, temperature, and other stresses that result in component failure or wear while many of the drivetrain components are in usable condition. In particular, automatic transmissions include one or more solenoid assemblies that operate by command of an electronic controller. These solenoid assemblies often have multipiece electrical connectors that provide power to actuate the solenoid and thereby operate the transmission. However, these solenoids can encounter wear or breakage of the electrical connectors that result in unreliable operation of the transmission, or complete failure to operate. Typically, these connectors are replaced, with the subsequent expenses of procuring new connectors and rebuilding portions of the solenoid assembly to incorporate the new connectors.
The Aisin Warner 55-50 (AW 55-50) transmission is a 5-speed automatic transaxle that is used by several automakers in front wheel and all-wheel drive vehicles. The AW55-50 is a computer controlled transmission that requires interaction between the computer and various sensors and solenoids. The sensors provide feedback to the computer in governing the shift strategy of the transmission. The solenoids are consequently controlled by the computer in order to command certain responses from the transmission. In the case of the AW 55-50, the solenoids are contained within the front control valve body (see FIG. 1). There are five solenoids (shift solenoids) that have two discrete states—on or off. There are an additional three solenoids (linear pressure solenoids) that have infinite states that range between full off and full on. These eight solenoids are all connected to the computer via a variety of wiring harnesses. A typical connection between the linear pressure solenoids and the wiring harness is shown in FIG. 2. In FIG. 2, the plastic male plug 1 from the wiring harness mates into the plastic female connector 2 on the linear pressure solenoid. The interlocking of the connection 3 can be seen in FIGS. 2 and 3 as well.
The locking features on the male plug and female connector can be further identified in FIG. 3. The male plug has a one-way tapered protrusion 4 extending beyond the top plane of the plug. The female connector on the linear pressure solenoid has a bridging feature 5 that intersects the protrusion 4 of the plug. During the engagement, the tapered edge of the protrusion pushes up the bridge allowing the plug to be inserted fully. However, the back edge of the protrusion mates flatly against the bridge 3 and therefore the plug cannot be easily removed.
The locking feature prevents servicing of the linear pressure solenoids without breaking the bridging feature on the connector. A service technician may try to insert a small screwdriver under the bridge as shown in FIG. 4. However, this often is ineffective because the amount of deflection required often breaks the bridge or permanently deforms the bridge. This renders the locking mechanism useless if the linear pressure solenoid is reused. Also, a service technician may just cut the bridge off the connector as shown in FIG. 5. Again, this prevents the plug from being secured in the connector if the linear pressure solenoid is reused.
Various embodiments of the present invention pertain to methods and apparatus to improve the repairability of used automatic transmissions.